It has been proposed to utilize multiple spark ignition with 4-cycle engines having removable cylinder heads. The use of multiple spark ignition provides a spark of greater duration and is believed to improve the efficiency of combustion. Most engines operate on a constant volume burn, and it is advantageous to ignite the charge at multiple locations.
The physical design of 4-cycle engines with removable cylinder heads allows the multiple spark gaps to be precisely arranged, but it is not possible to apply these concepts to an engine without a removable cylinder head due to the lack of means for establishing, and capacitively loading, the spark gaps within the combustion chamber.